The burning of coal, oil, and natural gas, as well as deforestation and various agricultural and
industrial practices, are altering the composition of the atmosphere and contributing to climate
change. These human activities have led to increased atmospheric concentrations of a number
of greenhouse gases, including carbon dioxide, methane, nitrous oxide, chlorofluorocarbons,
and ozone in the lower part of the atmosphere. The relative importance of these gases is shown
in